There is a market need for manufacturing metal-insulator-metal (MIM) devices in applications that require a high level of miniaturization. In such applications, the challenge is to address the materials and manufacturing techniques that will provide the MIM products with the desired performance characteristics.
Generally, there is a desire to manufacture MIM devices presenting a low equivalent oxide thickness (EOT) and/or low leakage current density (Jg), since, for example, the smaller the EOT a dielectric material can achieve at a certain leakage level, the higher the capability of the MIM device to store charges.
U.S. Patent Application No. 2011/0204475 A1, for example, discloses a method of fabricating a semiconductor stack with higher dielectric constant and conveniently low EOT. It is proposed to use a dielectric material, e.g., TiO2, in rutile phase in order to obtain a high dielectric value. Rutile is being formed after TiO2 deposition on a preformed layer, e.g., MoO2, with lattice matching characteristics, which can advantageously act as a template for the rutile TiO2 growth.
A different approach to improve the performance of MIM devices, e.g., MIM capacitors based on Ta2O5 dielectric, is disclosed in the article “Metal-insulator-metal capacitors' current instability improvement using dielectric stacks to prevent oxygen vacancies formation”, J.-P. Manceau et al., Applied Physics Letters, Volume 91, Issue 13, Dielectrics and Ferroelectricity, 26 Sep. 2007. This article discusses the reduction of leakage current instabilities due to the oxygen vacancies formed in the dielectric stack. More specifically, this article proposes the introduction of a thin stable dielectric layer, i.e., Al2O3, between the high-k dielectric, i.e., Ta2O5, and the electrodes, i.e., TiN, in order to prevent oxygen vacancy formation at interfaces.
A problem with the current techniques for manufacturing MIM devices is that oxygen vacancy suppression in the dielectric is not addressed.